SIGSEGV with nimrod finializers and echo

gistfile1.nim

type
  AObj = object
    b : BRef
  BObj = object
    i : int
  ARef = ref AObj
  BRef = ref BObj
      
proc finalize(a : ARef) =
  echo "A has gone"

proc finalize(b: BRef) =
  echo "B has gone"
  
for i in 0..500:
  var
    b : BRef 
    a : ARef
  new(b, finalize)
  b.i = 2
  new(a,finalize)
  a.b = b
  assert(a.b.i == 2)
  # weird behaviour with echo a.b.i
  echo a.b.i
  
echo "done"